Apparatus for casting zinc slabs and the like



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APPARATUS FOR CASTING ZINC sLABs AND THE LIKE Filed July 25. 1929 BH fahre d.

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May 23, 1933.

.the depth of the molten metal 2 is a tube 3. a valve casing 18 the removal Patented May 23, 1933 UNITEDk STATES PATENT oFFlCE DANIEL M. GRAY AND JOHN J. WILLIAMS, OF WHEELING, WEST VIRGINIA., ASSIGNOBS TO BLAZEL-ATLAS GLASS CO., 0F WHEELING WEST VIRGINIA, A CORTORATION OF WEST 'VIRGINIA Application led July 25,

This invention relates specifically to the casting of zinc slabs for use in making bottle closures, etc., but is also intended for use generally in the preparation of metal casting. 4

In the formation of metal castings' for the purpose mentioned it is not only desirable that the metal be as nearly pure as possible, but it is also important that the casting be practically free of blow holes and gas holes which cause material defects in articles prepared from such slabs.

In our copending application Serial No. 315,516, tiled October 27, .1928, now Patent No. 1,782,920 we have described an apparatus and method for casting metal slabs in vacuo so as to procure a more nearly pure metal and also to avoid the formation of gas holes and blow holes in the casting. An object of the present invention resides in certain improvements over our prior construction whereby the mold is disposed in a horizontal position when receiving its charge of molten metal, and whereby the use of heating apparatus, other than that employed in the conventional furnace, is practically avoided.

A further object of the invention resides 1n the provision of such an apparatus 1n which a suction force may bev applied to the mold cavity throughout the casting operation.

Another object of the invention consists in a method of casting metal in which the molten material is placed-in a vacuum chamber for a period of time prior to being discharged into the mold, thereby providing for of dissolved gases from the metal.

Other objects and advantages o f the invention will appear from the following description and attached drawing; in which c The 'figure is a vertical sectional view through the casting apparatus and .the forward part of the furnace to which it is attached.

The numeral 1 indicates the forward end of a furnace or tank in which the metal vis reduced to a molten state and refined prior to being cast or otherwise changed into useful products.

Mounted within thetank 1 and having its lower end disposed substantially midway of 1929. Serial No. 380,959.

This tube is preferably formed of stainless steel or other material which will not scale at high temperatures. Communicating with the' upper end of the tube 3 and also located within the furnace is a receptacle 4 also formed of stainless steel. The upper end of the receptacle or chamber 4 communicates by means of pipe 5 with a trap 6 for condensed vapors, gases, dust, etc., and this trap 1n turn communicates by means of pipe 7 with an air pump 8.

The tube 3 and the vacuum chamber 4.- surmounting the same are so proportioned that the upper portion of the chamber is substantially 56 inches above the normal level of the molten metal. It will be apparent therefore that so long as the system is vacuumized the molten Zinc willV extend up through the tube 3 and to a point substantially three quarters of the height of the vacuum chamber 4. This metal is of course, maintamed in its molten state by reason of the tube and chamber being located withinthe furnace structure, and the degree of heat surrounding these elements may be regulated by means of a damper 9 which communicates with the main Hue or stack 10. Furthermore, this construction in which the molten metal is subjected to avacuum in chamber 4 for i a period of; time affords an opportunity for entrapped and dissolved gases to escape from the metal.

Extending downwardly and forwardly from the bottom of chamber 4 is a second tube 11 of stainless steel. This tube extends through the wall of the furnace and preferably terminates in a flange 12 for cooperation with a similar flange on the mold to be described. For controlling the ow of metal through the tube 11 a valve 13 operable by a rack and pinion 14.-15 is provided. It is to be noted that this valve` is disposed within the furnace 1 a'nd that therefore there is no liability of the metal behind the valve becoming solidified with .a consequent clogging of the tube.

Connected in the vacuum line 5 `is a branch line 16 provided with a control valve 17. This tube 16 has mounted on its lower endinwvhich is located a holistv low steel ball valve 19 adapted to prevent molten metal from being drawn into the tube during the casting operation. Valve casing 18 is preferably surrounded by a hood 20 in which is placed a small burner 21 adapted to provide suhcient heat to prevent solidification of any metal entering the valve casing.

The extreme forward end of the furnace is provided with an open trough as indicated by numeral 22 and mounted thereabove are a plurality of horizontally disposed rollers 23 on which a mold 24 may be moved into position for cooperation with tubes 11 and 16. Any preferred type of truck 25 may be employed for transporting the molds to and from the conveyer 23, and a stop such as indicated at 26 is desirable for properly positioning the mold with respect to the elements 11 and 16.

Mold 24, in the embodiment shown, is provided with a neck or spout 27 terminating in a flange 28 adapted to register with the fiange 12 on tube 11 and to be secured thereto in a substantially gas-tight connection by clamps 29. The opposite end of the mold is provided with an opening 30 adapted to register with the opening in valve casing 18 and is held in substantially gas-tight relation therewith by means of suitable clamps and a gasket (not shown).

In the operation of the apparatus a column of the molten metal is maintained in tube 3, the lower portion of vacuum chamber 4, and the inner end of tube 11 by means of the pump 8. By this preliminary step in the method of casting it will be apparent that entrapped and dissolved gases in the body of metal which is to form the next casting is allowed to escape. The mold 24 having been placed in position and secured to the pipes 11 and 16 as heretofore described, the valve 17 is opened so as to permit the air in mold 24 and the lower end of tube 11 to be withdrawn. Valve 13 is now opened by rack and'pinion 14-15 and the molten metal allowed to descend into the mold 24; the vacuum line being maintained in operation so as to compensate for small leaks in the molds. As the mold fills the molten metal will float the valve 30 so as to cause it to engage its upper seat in `valve casing 18, thus preventing the entrance of the metal into the vacuum line.

The valve 13 is now closed so as to stop the further ow of metal through tube 11, and the clamps are removed from the connections between the mold and pipes 11 and 16. The mold is then transferred to the truck 25, and any metal remaining in the lower end of the tube 11 will flow into the trough 22 and be returned to the main body of molten metal in the furnace, While any metal within the valve casing 18 will be discharged to the Hoor of the factory, it being recalled that this metal will 4be maintained in a molten state by burner 21. It will be understood, of course, that during the discharge of the molten metal from the vacuum chamber yadditional metal will be forced up from the main body through tube 3 to take its place. This metal will in turn give up its dissolved gases and be ready for charging the next mold brought upto the furnace.

From the foregoing description and the attached drawing it will be apparent to those skilled in the art that we have provided substantial improvements in both apparatus and method of casting metal slabs; that by reason of the location of a considerable part of the apparatus within the furnace the necessity of additional heating apparatus is, to a large extent avoided; that the application of a suction force to the mold cavity throughout the casting operation compensates for leaks in the molds and produces a casting of higher grade; and that by reason of placing the metal in a vacuum chamber prior to its entrance into the mold, the metal is relieved to a large extent of entrapped gases and thereby tends to the formation of a casting practically free of blow holes and gas holes.

In accordance with the patent statutes we have described herein what we now believe to be the preferred form of our` method and apparatus for casting slabs; it is to be understood, however, that the drawing and description are intended as merely illustrative of the invention, and that the structure and methodof operation are susceptible ofvarious changes and modifications which are intended to be included within the scope of the appended claims.

What we claim as -new and desire to secure by Letters Patent is:

- 1. In an apparatus for casting metal slabs, a mold, a furnace, a vacuum system including a receiving chamber for raising the molten metal from the furnace, a tube for directing the raised metal from the receiving chamber to the mold, a connection between the mold and vacuum system for evacuating the mold, and a valve associated with said connection adapted to be automatically closed as the metal reaches a predetermined level in the mold.

2. In an apparatus for casting metal slabs, a furnace, a mold, means for discharging metal from the furnace into the mold, means for evacuating the mold, and a float valve in said means whereby the valve is automatically closed when the metal reaches a predetermined level in the mold.

3. In an apparatus for casting metal slabs, a furnace, a tube within the furnace and having its lower end submerged in the molten metal, a receiving chamber within'the furnace and communicating with the upper end ofthe tube, means `for creating a vacuum in .said chamber to draw metal from the furnace said chamber to draw metal from the furnace into the chamber and to remove gases from the metal therein, and means for conveying y,

molten metal from the chamber to a mold.

4, In an apparatus for casting metal slabs, a furnace, a tube Within the furnace and having its lower end submerged in the molten metal, a receiving chamber Within the furnace and communicating with the upper end of the tube, means for creating a vacuum in into the chamber and to remove gases from the metal therein, means communicating with said chamber and partly Within the furnace for conveying molten metal from the chamber to a mold, and a valve in said means within the furnace for controlling the How of metal to the mold.

DANIEL M. GRAY.

JOHN J. WILLIAMS. 

